Lathe attachment



March 31, 1931. H. L. DARDELET 1,793,143

LATHE ATTACHMENT Fild June 12, 1928 Patented Mar. 31, 1931 UNITED STATES PATENTsO'FFICE HUGUES LOUIS DARlDELET, OF NANTES, FRANCE, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO DARDELET THREADLOCK CORPORAT ,or DELAWARE ION, OF NEW YORK, N. Y., A CORPORATION LATHE ATTACHMENT Application filed June 12, 1928, Serial No. 284,700, and in France June 15, 1927.

My invention relates to lathes and to a method of turning elements therein.

"As is known in the art there exist screw cutting lathes, shaping lathes for millingtools having a regular section, lathes for reproducing members whose cross-section present various forms, and in which the tool is given an alternating movement regulated by a guide of suitable form, whereas the memher in question is given a movement of rotation.

If the section of the member is to follow a predetermined geometric line, the accuracy of the section of the member depends on the accuracy of the outline corresponding to the guide. In particular, if it is desired'to' ob- A tain sections in the form of Archimedes spirals accurately or other accurate curves, guides must be provided in the'form of acou- 2 rate Archimedes spirals or the other curve, which is followedoby the heel of the-tool'or toolpost which causes the extremity of the tool to follow an accurate Archimedes spiral. inthe turning plane of the member and by turning .plane of the member is meant the imaginary plane perpendicular to the axis of the lathe, rigid with the said member and-turd ing about the axis of the lathe. :The production of such guides is extremely fastidious not only by reason of-theprecision in outline which they necessitate, but also because of their process of manufacture which must be accomplished with rigorous exactitude.

It is the main object of my invention to' overcome these difiiculties and make possible the obtainment of members having the cross-section of. an Archimedes spiral, in a lathe, without previous outline.

The particularity of the process consists in this that the guiding assures feeding or displacement of'the tool in a direction perpendicular to the axis of the lathe, that is, to theaxis of rotation of themember to be worked which is established by a portion a spiral of a helix or thread of a screw, turning about an axis preferably perpendicular to the axisof thelatheand whose'extremi ties are joined in .a way to constitute a continuous guide path. Said spiral of a helix whose pitch is equalto the pitch of an A1:-

chimedes spiral which desired to be obtained is itself turned in a screw cuttin lathe without previousoutline.

There may thus be obtained members whose section, on the whole orin part, is an accurate Archimedes spiral, and may consist of one or several accurate Archimedes spirals, and in particular guides whosesections are accurate Archimedes spirals which may be subsequently used in reproducing lathes.

The invention will be readily understood by those skilled in the art to which it relates in the following given by Way of example front ele'vational view of a same guide, in accordance with the speedof rotation of the guide and the member being worked and in accordance with the angle that the frontcuttingto'ol rest vmakes with the axis of the lathe.

Referring to Fig. 1, on an ordinary type 0 known lathe is provided a toothed wheel a meshing, either directly or, as shown, through? the medium of one or more toothed wheels 6,

with a toothed wheel a, mounted on the extremity of the lathe spindle d, or with any other toothed Wheel of the lathe whose movement is derived from that of the spindle and which drives a plate 6 with drivingtapp'et f.

The shaft of said wheel a is mounted in'tw'o bearings 9 supported by a suitable bracket on the frame of the lathe. The wheel a transmits its movement, through the medium of a telescoping shaft 2' provided with universal joints j j to a beveled gear 70 whose shaft is supported by bearings secured to the carriage Z of the lathe. Said carriageis adapted to be given a displacement perpendicular to the axis of rotation m-m of the member being worked m which is supported in the usual manner between the head stock n and the tail stock n of the lathe.

With the wheel is meshes a wheel 0, having 5 the same or different beveling, whose shaft 0 is journaled in bearings likewise fixed to the carriage 1. The extremityof shaft 0 carries a guide 79, shown in detail and one larger scale in Figs, 2 and 3.

Said guide carriesa threadof'ajscreW' or spiral of a helix p constructed in the lathe and which extends through an arc slightly less than 360, the extremities of said" thread being interconnected by an intercalary: 1nem be tangent to the said extremities and to constitute with the thread, a continuous guiding path; It is on this guidingpath that the heel s of the tool post s 'in which isfixed atool t bears, under the action of a spring '2. tool holder slides in a bearing ofcarriage Z allowingdisplacement perpendicular to the axis iU-rifi' of the member being worked-to be when the guide 2 turns about the axis g y, while the member turns about'the-axis w w,

the heel slot the tool holder s 'bears on the screw 29 which being constructed in a lathe, 302 is accurate and the extremity t of the, tool it describes in the turning plane of the member (byturning plane is 'm'eant the imaginary plane rigid with the member mperpendicula'r to the axis jma9) an Archimedes-spiral u, of

3. accurate form" (Fig. 5) whose extremities M n are connected by a curve or rounded line a corresponding to the form of fitting of screw thread 70 01? guide 79. The pitch zlof said spiral(Fig.".5) is equal to the pitch? 40? of the screw thread in Fig. 2.

straight line contained in a plane passing through the ax1s,whose dlstance between perpendicular surfaces with respect to the axis- (represented by t Fig. 4) isatleast equalto the advance, per revolution of the member, of

thecarriage and of which the slope :on the axis w-m, represented by tan! ,8 (Fig. 4) fulfills certain conditions hereinafter poi nted out, there is obtained, with the same guide,

turned membersof diflerent form whose sections are elements of Archimedes spiral (Figs. 5 and 6) in accordance with the ratio of the speed of rotation'of the guide and of 55.

given tan. B.

The members thus obtained on the lathe are ber Q fitted to the guide p and whose surface g is of the shape of an S in-such a way as to,

Said

imparted thereto. Underfthese conditions,

If' he front cutting edge of the tool is 'a the lathe and in accordance"with the valuetion of the guide and g the advance'of the carriage per revolution of the member.

Suppose the circumference to be divided into 72 parts (n being more than 1 and as large as desired) and let m be the number of said parts of which the'rota'tion of'the member is advanced or retarded -on-=that-of the guide.

Let N be the number of elements of the Archimedes spiral of which the section of the body'is to be"composed.1l1j f Let Z be the pitch of the Archimedes spiralconstituting the cross section of the turned piece (Fig, 5).

Let Q, be the pitch of the piece turned. Let ,8 be the angle to be given the front cutting edge ofthetool withrespectjto the axis of the lathe; which edge is contained-in P P g th ough 'saidaxisKFig;

, v i 85 a 1 1 ratio of the speed of theguide andthatofthe e ber: I:

qyninl" ewe ltwillbe noted that n, 'g and Q constant and-that it is merely necessary to vary N for obtaining 'helicoi'dal '-bodies 4 of different pitch andgdifle'rent numberof threads, I that is, whose section is eomposed of a number of di-fi'erent spiral elements.

Right cylinders being merely a particular case ofhelicoidal bodies where the pitch Q, is infinite and thean-gle ,8 zero, it' will be seen that Zright cylinders will be obtained "having anumber of-Archirnedesspiral-elements in cross section-lwhen the following, relation;

existsz is the ratioi of the speed of the guide *There; are thusv ob-.-

that of the member; tained right cylinders only when said ratio of speeds is a whole number, provided that the angle B has a value of zero','that is, that tothe axis. i a a A few concrete examples of the'above the; oryjwill now'be given. Y r W Suppose the threaded guideto the'left :is rotated to the right and that the member turns in a counterclockwise-direction with thefront cutting edge of the tool is parallel respect to an observerhp'laced at thefhead stock 41, and that theicarri'age -is displaced 'in the direction of the tail stock to; head stock- Suppose the guide'to have a pitch of2 4 mm. and that the advance of the carriage per revolution of the guide be mm.

Suppose also that the circumference be divided into 12 equal parts and that the rotation of the member be lagging 5 of said parts per revolution of the guide, that is, that the ratio of guide speed and the member speed stock, that is, the cutting edge of the opening is disposed as indicated at t in Fig. 4.

There may be obtained other sizes remaining equal, but by giving to the tangent B the value of .2 the opening of the angle being turned towards the head stock, that is, the tool remaining disposed in a position inverse to that of Fig. 4, a helicoidal body whose pitch will be 24 mm. to the right and whose section will be composed of two elements of spiral form having a pitch of 48 mm.

Another example, with the same pitch of the guide and same advance of the carriage, suppose the circumference to be divided into two equal parts and the member lags the uide a distance of two of these parts, there is obtained a right cylinder whose section is composed of two symmetrical spiral Archimedes elements whose pitch will be .418 mm., if tangent B is given a value equal to zero,

/ that is, if the front cutting edge of the tool is parallel to the axis, since But if there is given to this angle a value such whose pitch to the right is 40 mm.

If the length of the front cutting edge between two lines perpendicular to axis w-a:

that is, IE is at least equal to the advance, per revolution of the member, of the carriage and if the angle B has been given a suitable value, the. surfaces of the turned members will be smooth in the part where the section is a spiral, but not in the part of the fitting. In the opposite case the surfaces,

in the part of spiral form will be streaked with threads corresponding to the form of the extremity of the tool and whose pitch is are to be put, the said grooves maybe removed by milling or grinding.

After having produced anarcuate Archimedes spiral according to the process above described, it may in turn be used as a spiral guide for turning a whole series of members.

While I have described what I. deem to be the preferable form of my invention, I do not wish to be limited thereby since changes might be made in the details of construction and arrangement of parts without departing from the spirit of the invention as comprehended within the scope of the appended claims.

Having described my invention what I claim as new and desire to secure by Letters Patent is 1. In a lathe having a carriage and a tool post slidable on the carriage toward and from the work, the combination with the carriage and tool post of a driven shaft disposed at right angles to the turning center of the lathe and journalled on the carriage, a tool post retracting spring connecting the tool post and carriage, a hub mounted on said driven shaft to turn therewith and carrying on its perimeter an integral helicoidal rib extending less than a full turn and having the form of the rib of a screw thread of constant pitch, the tool holder having a part held to one face of said rib by said spring, and a filler piece secured to said hub between .the ends of said rib and having a side surface merging at its ends with that side surface of the rib which coacts with the tool holder.

2. A tool advance and retraction controlling cam for lathes comprising a hub having an integral helicoidal rib on its perimeter corresponding with a partial turn of a screw thread rib of uniform pitch, and a filler piece held between the ends of said rib and having one side face merging at its ends with the ends of one side face of the rib to form a continuous guiding surface at one side of the rib.

3. A tool controlling cam as claimed in claim 2, wherein the specified face of the filler piece curves in opposite directions from ap-' proximately mid-length thereof to its lines of merger with the specified side face of the rib.

In testimony whereof I have signed this specification.

HUGUES LOUIS DARDELET.

equal to the advance of the carriage per revolution of the member. Obviously when the members are streaked with threads their cross sections are no longer spirals of accurate Archimedes form. If the grooves on the fitting part (that between a a Fig. 5) are undesirable in the use to which the members 

